Words by Ellen Peirson
The use of hemp as a material was once so routine that it pervaded the production of rope, ship sails, fabrics, paper and medicine. In fact, it was seen as such a necessary crop that under the reign of Henry VIII, it was compulsory to grow a quarter acre of hemp for every 60 acres of cultivated land, out of fear of running out of such an essential resource. Outlawed in 1928 due to its connotations with narcotics, its possibilities went unrealised for decades, as chemical-based products flourished instead.
The natural, clay-coated texture of hempcrete is complemented by the exposed timber frame and staircase. Image credit: Oskar Proctor
Now, as we look to ways to address the urgent climate crisis, hemp cultivation is legal again, and its opportunities are slowly being discovered — or rediscovered. At Margent Farm, a 21ha hemp farming facility in Cambridgeshire, Practice Architecture and Material Cultures have recently designed a 100 sq m house from the industrial hemp growing in the fields surrounding it. The design brings together an ancient crop with modern construction techniques. Timber panels were prefabricated off site and filled with a mulch of hemp, lime and water, commonly known as hempcrete — so-called because of its similar composite materials to concrete, using lime as a binder.
After being erected on site in just two days, the dried product has created highly insulated walls, to which hemp fibre-based corrugated sheets have been fixed.
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Built from the crops surrounding it, Flat House feels like a product of its landscape. Image credit: Oskar Proctor
The hemp plant actually sequesters carbon from the atmosphere as it grows, simultaneously replenishing the soil as leaves fall to the ground and decompose. The hempcrete block itself is a natural thermal mass, storing heating from the sun and internal heating which it then diffuses into the space as it cools. The hemp products used in construction came from the farm’s first-ever crop and are part of wider ambitions to bring the plant back into use. Together, the architects and Margent Farm co-founders Fawnda Denham and Steve Barron have a dream of getting hemp into mainstream building. To do this, they decided to be immersed in the process: ‘We wanted to live on the land, through the seasons, to understand what we were trying to achieve here,’ Denham explains — and for this they built Flat House.
The exposed materials create a warm palette that balances with the calm landscape outside. Image credit: Oskar Proctor
In this sense, the whole project is an experiment, and this is visible in the architecture. As part of ongoing research into the properties of hempcrete and its different applications and aesthetics, the architects incorporated a number of panels made using commercial hempcrete, to understand the application of a much more regular form of the material. ‘The hemp that we got from the farm has got quite a lot of fibre in it and variation in the length of the shive, which actually I think really improves the integrity of the hempcrete,’ explains Paloma Gormley, founding partner of Practice Architecture. ‘The commercial hemp is completely free of fibre and very regular lengths, so you get a much more uniform finish.’
Gormley recently joined forces with architect Summer Islam to form Material Cultures, a non-profit organisation researching building systems with natural materials and how these can be manufactured at scale. ‘We are taking on the area of research of what it means to apply natural and grown materials to off-site construction and factory-made housing,’ says Gormley.
The hempcrete acts as a natural thermal mass, storing heat from the sun and internal heating which it then diffuses into the space. Image credit: Oskar Proctor
Flat House sits within the boundaries of a steel-framed shed and as such was approved under permitted development rights for agricultural buildings. As a result, the house is small, but a double-height living area and a large, glazed conservatory create a generous set of spaces.
The conservatory provides a sense of openness and connection with nature. As you move through the spaces, into the living area and up to the bedrooms on the first floor, it slowly becomes more intimate and more enclosed. While the design of living spaces is necessarily constrained by the boundaries of the shed, the exposed hempcrete panels become the leading feature.
The double-height living area and large, glazed conservatory create a spatial generosity. Image credit: Oskar Proctor
In the image of an agricultural vernacular, and built from the crops surrounding it, Flat House feels like a product of the ground it grew from. On some of the panels, a hemp plaster has been applied. ‘We’re interested in testing out different finishes, so the idea is that the entire house could be plastered internally depending on your aesthetic taste,’ says Gormley. ‘We went for the [panels] in the bathroom as a way of testing that finish, in a complete space.’ Flat House was simultaneously designed as a bespoke farmhouse and as a vehicle to understand how hempcrete can be used at scale and as part of conventional building techniques.
The house itself encompasses this exploration of the material and its potential applications. The majority of the prefabricated timber panels are left exposed, sprayed with a thin clay paint that both contains the dust and creates a slightly more finished surface to the product which can be somewhat crudely processed. With a clay coating, the natural texture of the hempcrete is complemented by the exposed frames of the timber panels. Together, the materials bring a solidness that framed buildings usually evade and the exposed materials create a warm palette that balances with the calm landscape outside.
Floor-to-ceiling windows give a sense of openness and connection to nature. Image credit: Oskar Proctor
Viewing Flat House from the winding track that approaches it, it seems like any other auxiliary agricultural building. The large structure blends into the landscape, occupying the space of a previous barn. With a three-inch profile corrugated panel, the exterior can seem commonplace, even unremarkable. These panels were in fact the result of extensive prototyping by Gormley and Margent Farm in developing a sustainable hemp-based product, durable enough for exterior use. Of the development process, Gormley said: ‘We looked at bio composites that are pre-existing, testing a spectrum of resins and different fibres, such as flax and hemp and then we got very excited about this sugar-based resin because, similar to the hemp, it’s agricultural by nature and it’s also derived from agricultural waste.’
Flat House seems so simple in its design, with its construction expressed truthfully. It’s plain to see what’s holding the house up. You can see the materials that are keeping it warm; you can even see where the hemp came from. Yet its design is part of a much more rigorous endeavour undertaken by Material Cultures. ‘We’re looking at scaled versions of [Flat House],’ says Gormley. ‘We’re talking to lots of developers about sites across the country and doing research in further demonstrating and developing different panel systems with the intention of being in a position to build.’ Sitting in the living area of Flat House, it’s easy to forget that it is part of this bigger picture — preferring to be embraced by the vast landscape that created the walls and is now framed by them.